638978813 has 8 divisors (see below), whose sum is σ = 738072000. Its totient is φ = 546719680.

The previous prime is 638978773. The next prime is 638978827. The reversal of 638978813 is 318879836.

638978813 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638978813 - 2¹⁸ = 638716669 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638978833) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1708313 + ... + 1708686.

It is an arithmetic number, because the mean of its divisors is an integer number (92259000).

Almost surely, 2^638978813 is an apocalyptic number.

It is an amenable number.

638978813 is a deficient number, since it is larger than the sum of its proper divisors (99093187).

638978813 is a wasteful number, since it uses less digits than its factorization.

638978813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3417027.

The product of its digits is 1741824, while the sum is 53.

The square root of 638978813 is about 25278.0302436721. The cubic root of 638978813 is about 861.3152818692.

The spelling of 638978813 in words is "six hundred thirty-eight million, nine hundred seventy-eight thousand, eight hundred thirteen".